“Your support has helped me enormously,” Van der Laan said. “It was a great privilege to be the mayor of the nicest and prettiest city in the world.”

He went on to thank all Amsterdammers for placing their trust in him for the past seven years, and for working with him in times of both agreement and dissent.

Netherlands Prime Minister Mark Rutte reacted to the letter quickly on Twitter, calling it "very sad news," and expressing "admiration for his courage and openness." Rutte added that the whole country "empathizes with him and his family."

The popular mayor was given a 7.7 score on his job performance by the public in 2015, which the Volkskrant noted as being particularly high. However, the mayor was told he could no longer carry on his job function by his doctor, Van der Laan said. His health had been the subject of rumors around city hall for quite some time, particularly after his appearance this summer in a wide ranging interview on Zomergasten that drew over a million viewers.

"I've been in pain for some time. But that's how it goes, the cancer comes from all sides. But I'm not feeling so tired right now,” he said on the NOS broadcast in July. "Sometimes I'm overcome by fatigue.”

Van der Laan officially notified the King’s Commissioner of his decision to resign, he said in the letter released on Monday.